JPMorgan Chase's website went kaput yesterday when the bank became the latest US financial institution to find itself on the business end of a distributed denial-of-service assault.

Visitors to chase.com were shown a "website temporarily down" message on the front page, although the bank's mobile apps were said to be working.

Iran and a group of Islamic activists called the Izz ad-Din al-Qassam Cyber Fighters have been linked to internet attacks on major American banks, including US Bancorp, Citigroup, Wells Fargo and Bank of America.

"In new phase, the wideness and the number of attacks will increase explicitly; and offenders and subsequently their governmental supporters will not be able to imagine and forecast the widespread and greatness of these attacks," the group said in a statement posted on the Pastebin website in December.

the Cyber Fighters said that the reason for the computer network offensive was the continued availability of the inflammatory Innocence of Muslims video on YouTube. However, when the video was taken down, the group said it had suspended its attacks.

A former American government official claimed earlier this year that Iran was orchestrating the attacks. James Lewis of the Centre for Strategic and International Studies in Washington believed that the aim was retaliation over the nuclear-fuel-centrifuge-knackering virus Stuxnet and other cyber-barrages against Iran.

JPMorgan Chase's site now appears to be working, although DDoS attacks can result in intermittent service. In December, Wells Fargo customers had trouble using the bank's site for at least four days as it dropped in and out of view. But security experts have said that there's no real evidence to show that Iranian officials are behind the campaign. ®